This kind of concealed slide fastener has been often used for women's clothes. The concealed slide fastener has, however, been applied to other fields, for example, a passenger seat of an automobile or a train in recent years. In the passenger seat, the cushion body formed integrally with a frame in advance is covered with a seat cover. At this time, the size of the seat cover is set smaller than the external dimension of the cushion body, so that the cushion body is covered with the seat cover under the compressed state so as to suppress looseness and deformation which may occur in its external shape as much as possible. Further, in order to easily cope with the load distribution of a human body when the passenger takes a seat, the seat cover allows the cushion body, even if it is elastically deformed, to reliably restored to its original shape when the passenger leaves the seat, thereby preventing the cushion body from deformation.
The seat cover is typically made of a sheet in which an outer layer, a thin elastic intermediate layer and a back base fabric layer are integrally laminated by the laminating process etc. The outer layer is comprised of a natural leather, a synthetic leather, or a knitted/woven fabric having various structures. The intermediate layer is comprised of a polyurethane foamed sheet or the like. The back base fabric layer is comprised of a thin knitted/woven fabric or the like obtained by weaving or knitting using extremely thin yarns. This sheet is typically cut into a plurality of sheet pieces according to the shape of a passenger seat, and these sheet pieces are sewed together three-dimensionally to produce a seat cover. However, if the entire seat cover is manufactured by sewing, a cushion body having a complicated external shape may not often be covered with the seat cover. For this reason, up to now, a part of the seat cover is not sewed in advance. After the seat cover is covered on the cushion body, the non-sewed part is sewed by hand.
However, in this sewing process based on the sewing by hand, the finished products are apt to be different in quality or sewing time depending on a difference of the skill of a sewing operator. As such, to eliminate the sewing by hand, a slide fastener, particularly a concealed slide fastener whose slider body is not exposed to the outside, has recently been often used along a part, e.g. a seaming part, of the sewing section of the seat cover. As a result, the entire sewing process can be carried out by a sewing machine, so that the conventional faults based on the skill difference are considerably reduced, and the productivity is further improved.
As such a conventional concealed slide fastener, as disclosed in, for example, Patent Document 1, there is used a slider including left and right side wall portions erected from left and right edges of a lower blade of a slider body, left and right first flanges extending from upper ends of the side wall portions in a mutually approaching direction, a guide post erected on a central portion of one end of the lower blade in a sliding direction, a second flange protruding outwardly along an outer circumference of the guide post, and a pull-tap attaching post provided on a top surface of the second flange.
A space defined by the first flanges, the guide post and the second flange becomes a guide passage of an engaging element row, and gaps formed between the first flanges and the second flange serves as a guide gap for fastener tapes. On the other hand, in fastener stringers that are inserted into the slider having such a configuration, a plurality of engaging elements are attached along opposite side edges of a pair of fastener tapes by sewing or the like, with their meshing heads positioned inside. An element attaching edge of each of the pair of fastener stringers obtained in this way is bent in a-U shape such that the meshing head of each engaging element protrudes to the outside, and then is fixed in the bent shape by thermal setting. The pair of fastener stringers having such a structure are inserted into the slider by causing folded portions of the fastener tapes to extend outwards through the tape guide gap between the first and second flanges with the meshing heads of the elements being opposite to each other in shoulder mouths of the slider. Thereby, a concealed slide fastener is obtained.
Here, when the concealed slide fastener is applied to the seat cover of the passenger seat of the automobile as mentioned above, a strong lateral pulling force is applied to the fastener stringers in the vicinity of the slider because the seat cover is formed so as to be smaller than the external dimension of the cushion body. The engaging elements stand up due to the strong lateral pulling force. Each element, which is introduced into the shoulder mouths of the second flange while its part near the shoulder mouths is placed under the lateral pulling force, stands up until it becomes approximately perpendicular to a tape surface of the fastener tape.
For this reason, in the slider for the concealed slide fastener disclosed in Patent Document 1, an upper end ridge of a taper surface of the second flange on the side of the shoulder mouths is set to be higher with respect to the lower blade than that of a rear mouth, so that the elements are guided along the taper surface of the second flange without interfering with the second flange although the elements are mounted on the lower blade in a slightly tilted posture, and thus are introduced into the element guide passage of the slider. During the introduction, the elements are subjected to the overall influence of the guide by the taper surface, and a tilting force caused by the pulling force of the preceding elements and the fastener tapes, and thus are gradually inclined so as to take a posture in which coupling portions of the elements attempt to crawl into a lower surface of the second flange, and prevents the meshing heads of the elements from being nipped between the first and second flanges of the lower blade, thereby promoting smooth sliding of the slider.